This invention relates to a novel decalcomania and to a method for incorporating the decalcomania design onto a ceramic article. The decalcomania has a novel paper backing and can be applied directly to unfired greenware without removal of the paper backing. The method requires no heat treating or firing of the ceramic article prior to fixation of the decalcomania and requires only one firing step following fixation of the decalcomania.
In the transfer of a decoration from a decalcomania to a ceramic material, it has been general practice to prefire the ceramic material to form a bisque and then to apply the decalcomania to the bisque. It has been customary to either remove the paper backing from the decalcomania upon setting the decalcomania onto the earthenware or to apply the decalcomania together with its paper backing and then to fire the article containing the decalcomania to burn away the backing before adding the glaze. Glazing occurs by spraying or dipping a glazing material followed by a firing step. Therefore, when the paper backing was not preremoved, it was customary for the ware to undergo two firing steps before spraying the glaze onto the decalcomania. The first firing step was the preparation of the bisque and the second was the burning of the paper backing.
According to the prior art, in the application of a decoration, pattern or logo to a ceramic or pottery article, there are several methods and types of decals that are commonly used to obtain the desired end product Prior art decals generally have a paper backing, a layer containing ceramic pigment powders in an organic base, and a top layer that is also organic which can also contain small amounts of ceramic fluxes. One prior art method of decal application is performed by first moistening the decal in water to enable removal of the paper backing, in which case the decalcomania used is commonly referred to as a water mount or slide-off decalcomania. Another prior art method of decal application is performed by moistening the decal in a solvent to enable removal of the paper backing, in which case the decalcomania used is referred to as a solvent mount decal. When the paper backing is removed from a prior art decalcomania, the organic base containing the ceramic pigment powders and the top organic layer remain intact so that the image, decoration, or pattern can then be transferred to the ceramic article and bonded to the surface by a method commonly referred to as "squeegeeing". The organic layers of the prior art decal do not allow proper glazing to occur unless they are first fired at a temperature sufficiently high to volatilize and drive off the organic layers and fuse the ceramic powders to the article. This procedure is called "hardening-on" and is time-consuming, costly and labor intensive and, thus, increases costs for each article decorated.
U.S. Pat. No. 3,860,471 outlines the following criteria which must be met in order to have a satisfactory decal system in a manufacturing atmosphere.
1. The decal must have sufficient body to stay in place on the ware, particularly when being applied to curved or irregular shaped surfaces.
2. The decal should flow smoothly when applied to the ware, e.g., by squeegeeing.
3. The decal should have good covering properties and leave no uncovered areas.
4. The bonding medium underneath the decal should not bond so quickly that the position of the decal cannot be adjusted on the clayware article.
5. The bonding medium must have sufficient bonding action to seal the decal to irregular or curved surfaces.
6. The bonding medium must insure adhesion of the decal during glazing and firing.
7. The bonding medium is preferably water soluble or water miscible so as to permit cleaning of work areas without the use of organic solvents.
8. The decal should allow the application of glaze over its surface to be equal in thickness to all other areas on the article being glazed where there is no decal present.